In general, oscillating tools are light-weight, handheld power tools capable of being equipped with a variety of tool accessories and attachments, such as cutting blades, sanding discs, grinding tools, and many others. These types of tools typically include a generally cylindrically-shaped main body that serves as an enclosure for an electric motor as well as a hand grip for the tool. The electric motor oscillates a spindle having a tool holder to which any one of various accessory tools may be attached. As the spindle is oscillated, an accessory tool attached to the tool holder is driven to perform a particular function, such as sanding, grinding, or cutting, depending on the configuration of the accessory tool.
Oscillating tools include an oscillating drive that converts rotational movement of the output shaft of the motor to an oscillating movement that is used to drive the spindle. In most previously known oscillating tools, the oscillating drive uses an eccentric mechanism for producing the oscillating movement. For example, in some tools, the output shaft of the motor is received in an eccentric bearing. In other cases, the output shaft of the motor includes an eccentric drive pin that is received in a normal bearing. In either case, the spindle is held by a fork structure that is mounted onto the bearing and that extends from the bearing to position the spindle in front of the output shaft. As the output shaft is rotated by the motor, the eccentric bearing or the eccentric drive pin shifts the fork from side to side which causes the spindle to oscillate.
While effective, eccentric drives for oscillating tools are limited in the amount of stroke that can be generated, the size of the blade that the tool can be effectively driven, and the inertia of the blade. In addition, oscillating drives are susceptible to vibrations caused by the oscillating mass of the oscillating mechanism. The vibration introduced is a combination of the inertia of the mechanisms along with the movement of the center of gravity of the mechanism. Eccentric drives have a configuration that makes it difficult to drive a counterbalance to counter the vibrations caused by the oscillating mechanism. Eccentric drives are also faced with the issue of loss of stroke due to flexing of the housing. Under heavy cutting loads, the housing of the tool can flex, causing the output stroke of the tool to be reduced. This impacts tool performance. To address this issue, some oscillating tools have been provided with reinforced housings which can increase the cost of the tool.
What is needed is an oscillating drive for an oscillating tool that is robust, is less susceptible to vibrations, can handle heavy cutting loads without a reduction in stroke, and can be easily counterbalanced and that does not require an increase in the size or dimensions of the housing to accommodate the drive.